I like it, but minor note: the Observer Effect is actually a very well-understood phenomena that doesn't rely on human cognition. That belief is what's sometimes called 'quantum mysticism,' a misreading of the science basically equating quantum mechanics with magic. Anthropomorphization of physics.

I realize that, but this is fiction. I'm not saying magic is real, I'm just saying the magic that exists in my Head-canon is based largely on quantum woo.

Basically, you start with the premise that consciousness can influence reality directly via collapsing quantum wave functions (I realize this a fringe theory among actual scientists, but I don't think it's actually falsifiable)1. Normally this effect is atomic in scale, but that's because the EVE is diffused in every direction and incoherent, like light from a bulb. Thaumaturgy uses ritual to focus a person's EVE like a laser beam, amplifying it to perform work at a human scale.

There's also the Hume Field, which holds the laws of physics in place. It gives things reality just like the Higgs Field gives particles mass. In times and places where the Hume Field is weak, it's easier to violate the laws of physics and perform thaumaturgy. Reality Benders don't interact with the Hume Field as strongly as normal, and are thus able to use their EVE for magic more or less at will.

Footnotes

1. This effect is also what allows consciousness to transition to other planes of existence/mediums upon brain death

Obviously, that's fine. But, no, they proved that human cognition doesn't effect particle-wave duality, or the Turing Paradox, or any of the stuff that people like to attribute mystic qualities to. Physicists often get frustrated by quantum mysticism, as it's a deliberate misread and sensationalization of a real and well-understood phenomena.